1. Field of the Invention
The present invention relates to an aqueous ammonia composition having low surface tension that is useful, for example, for cleaning substrates in the field of semiconductors. More particularly, the present invention relates to an aqueous ammonia composition having low surface tension, which contains a specific fluoroalkylsulfonamide, and that is suitable as a cleaning agent to be used in the semiconductor industry.
2. Description of the Prior Art
With the development of the electronic industry, various semiconductor elements are designed and manufactured. These semiconductor elements generally use silicon wafers as a substrate. In the process for manufacturing semiconductors, ammonia water is used in combination with other substances for cleaning silicon substrates, especially to remove microparticles therefrom and to eliminate residual matters after resist ashing.
In recent years, the density of integrated circuits has been increased to induce more minute and complicated patterns. The use of conventional ammonia water, which has high surface tension, in such case inevitably gives rise to trouble in cleaning, such that removal of microparticles lodged in gaps between the micropatterns becomes difficult.
RCA-cleaning was reported by W. Kern et al.: RCA Review 31, PP 187-205, June (1970) and has been widely utilized in the semiconductor industry. In the RCA-cleaning, a mixed solution of ammonia water and an aqueous hydrogen peroxide is usually used, the proportion of such mixed solution typically being one part ammonia, one part hydrogen peroxide, 6 parts water in terms of volume ratio.
In cleaning a silicon substrate with the RCA-cleaning solution, however, the following problems have been associated with using the mixed solution:
(1) Particle adhesion PA1 (2) Microroughness PA1 (3) Metallic adhesion.
As a result, the treated substrate becomes coarse and permits the formation of fine pits, which cause deterioration of the resultant semiconductor element.
Accordingly, it is desirable to develop a new type of aqueous ammonia composition that overcomes drawbacks of the prior art conventional solution, that has a low surface tension, and that produces a remarkably increased cleaning performance without damaging the surface of the substrate.